Modern mining technology involves automatic and remote-controlled machines, which can be controlled and monitored from control rooms located below or above the ground. Remote-controlled machines include mainly various drilling, loading and transportation machines. In particular, remote-controlling improves the working environment of the personnel. The remote-controlling and other kind of data transfer require a remote-control system for transferring data between machines and control rooms.
Machines have typically been controlled over a wireless connection. The path of the remote-controlled machine is provided with a sufficient number of base stations so that information, for example control data to the machine and video data to the control station, can be transferred continuously between the machine and the control room. The machine comprises a terminal at least for receiving a radio signal, and typically also for transmitting one. To maintain the data transfer connection, the base station responsible for data transmission, i.e. serving the machine, has to be changed as the machine proceeds.
A wireless connection has usually been implemented utilizing proprietary data transfer methods. A prior art radio interface of a system employs the spread spectrum technique, which provides a data transfer link for transferring data, video and audio signals combined into one digital bit stream.
The use of generally standardized data transfer techniques in the remote control of machines has also been contemplated. For example, the WLAN technique (Wireless Local Area Network) standardized by the IEEE, in particular IEEE 802.11 based techniques have been proposed for this purpose. A problem associated with WLAN techniques as well as with some other wireless packet-switched data transfer techniques is how to provide a sufficiently reliable data transfer connection so that data transfer delays remain sufficiently small for reliable remote controlling.